1. Field of the Inventionxe2x80x94This invention relates to an article of manufacture and method. More specifically, this invention relates to a system, incorporating a unique retaining gland and seal design, for rotary shaft sealing and to a method for sealing a rotary shaft. The system of this invention is suitable for high pressure sealing applications, specifically, for sealing of the rotary shaft of pumps and motor seals for automotive, marine, agricultural and industrial applications.
2. Description of the Prior Artxe2x80x94Cartridge rotary seals have been used for many/years in a variety of applications for the sealing of various types of fluids and gases. The function and purpose of such seals includes containment of fluids (lubricants) within the internal environment associated with a rotary shaft, and the exclusion of foreign matter from the external environment from contamination of such lubricants.
Generally, these seals comprise a solid elastomeric/flexible body supported in metal (retaining gland). Typical seal materials utilized in this sealing environment include fluorocarbon polymers, for example, polytetrafluoroethylene, (PTFE), because they exhibit relatively low friction, are chemically inert, and can withstand a variety of temperatures. Moreover, because these materials have self-lubricating properties, they can be used to form a coherent and compliant seal with a rotary shaft with little or no additional lubrication or sealant. Such prior art cartridge seals generally have the elastomer in a bonded relationship with a circular metallic ring (e.g. garter) which can also vary as to geometry. In practice, the metallic portion of the seal is pressed into a housing while the elastomeric seal bears around the rotary shaft. As herein above noted, when plastics are utilized, such as fluoropolymers, the plastic is bonded to the metallic ring and the entire assembly is pressed into the housing (gland) with a degree of interference between the outside diameter (OD) of the seal and the housing to permit retention of the seal assembly within the housing, and, at the same time, provide static sealing of the housing. Dynamic sealing between the seal and the shaft is provided by the elastomer""s pressure contact with the shaft. A common problem with such seals is improper bonding between the plastic and the metal which, when subjected to chemical attack and elevated temperature, causes loss or distortion in dimensional stability of the seal under load, resulting in leaking.
U.S. Pat. No. 6,050,572 (to P. J Baisells, issued Apr. 18, 2000) describes a rotary cartridge seal including a separate plastic ring and retainer which are uniquely locked together so as to reportedly provide a residual force therebetween in order to maintain the components together within specific (elevated) temperature parameters. The Baisells system contemplates placement of the seal within an open retention gland; and, the reliance upon the retainer ring for sealing engagement of the seal relative to a rotary shaft. Notwithstanding such improvement, the Baisells device is apparently exclusively reliant upon the materials component of the seal (Teflon(trademark)) to provide lubrication at the interface of the seal and the rotary shaft; and, upon a retainer ring for maintaining sealing pressure between the seal and the shaft. Baisells does not specifically address the use of his seal in a high pressure sealing environment, and, thus, the effects of elevated fluid pressure and/or pressure surges upon his seal are neither contemplated nor known.
U.S. Pat. No. 6,050,570 (to D. L. Otto, issued Apr. 18, 2000) describes a seal for an anti-friction bearing (FIG. 2) wherein the primary sealing element comprises a composite of two mechanically and, optimally, chemically distinct materials, (col. 4, lines 36). The resultant composite is described as having a primary element (reference numeral 28) and an insert (reference numeral 66). The Otto seal is further characterized as self-lubricating because the contact lip of the seal insert (reference numeral 66) is formed of polytetraflouroethylene (Teflon(trademark)). The Otto seal is designed to retain grease within the race of a roller bearing, and to isolate the race from contamination by the external environment. It would appear that the fluid dynamics of grease in the roller bearing of the Otto seal is not particularly demanding, nor does it appear that the seal is exposed to pressure surges of lubricant or lubricant pressures which could potentially result in the leakage of lubricant at the contact lip of the seal. Ott does not specifically address the use of his seal in a high pressure sealing environment, and, thus, the effects of elevated fluid pressure and/or pressure surges upon his seal are neither contemplated nor known.
U.S. Pat. No. 6,050,571 (to G. Rieder, et al, issued Apr. 18, 2000) describes a sealing arrangement for a bearing bushing, specifically, a sealing arrangement for a bearing mounted pin of a cardan joint (FIG. 1). The Rieder sealing arrangement (Col. 3, line 43 to Col. 4, line 6) comprises a rotary shaft seal (reference numeral 2) with an integrally formed sealing lip (reference numeral 9). The Rieder sealing arrangement contemplates the force fitting of the seal (reference numeral 2) between an armoring (reference numeral 3) an inner wall (reference numeral 4) ofbearing bushing. Rieder has further provided/located an additional seal or a fore-seal (reference numeral 5) upstream from the rotary seal. The fore-seal is intended to bridge a gap between a pin (reference numeral 6) and the bearing bushing (reference numeral 1). The stated design objective of the Rieder system is to provide an extended sealing lip at the interface of the seal and rotary shaft, which the Rieder contends improves the sealing pressure at the interface of the seal and the shaft. Rieder does not specifically address the use of his sealing arrangement in a high pressure sealing environment, and, thus, the effects of elevated fluid pressure and/or pressure surges upon his sealing arrangement are neither contemplated nor known.
Also, for unsprung lip seals, the lip relies on the lip stretch around the shaft to give initial sealing and as fluid pressure increases the initial elastomer load is insignificant. If fluid pressure on the lip causes high frictional heat as the shaft rotates, the rubber heat ages and sets to shaft size. This invention addresses this issue by controlling fluid pressure on the lip and thus reducing heat aging of the rubber.
As is apparent from the foregoing discussion, the configuration of a retention gland and the associated design of a rotary shaft seal, not only determines the effectiveness of the seal, but also its resistance to displacement in the course of use, specifically, its resistance to variable conditions (torque, pressure surges, temperature changes, etc) encountered during use. Thus, it is both critical and essential that each of these seal components be resistant to environmental conditions and support the physical integrity and performance of each other under such variable conditions. While such objective is both desirable and apparent, the achievement thereof is beset with numerous probes, including the potential for wear associated with the relative movement (both axial and rotational) of each of these components, a breakdown in the self-lubricating properties of the sealing materials, controlled access of lubricant to the shaft seal interface; and the, maintenance of critical tolerances of these components within this demanding environment. Generally, the prior art efforts made to accommodate this demanding environment (which have indeed been limited) traditionally involve a series of compromises and, thus, a sacrifice, of, for example, sealing performance in order to extend service life of the seal or visa versa. Accordingly there continues to exist a need to resolve these competing design and performance criteria, without compromise in seal integrity and durability.
It is the object of this invention to remedy the above as well as related deficiencies in the prior art.
More specifically, it is the principle object of this invention to provide an improved radial lip seal which is suitable for use in high pressure (20 psi or greater) sealing environments.
It is another object of this invention to provide an improved radial lip seal that is suitable for use in high pressure (20 psi or greater) sealing environments, wherein surges or variation in pressure can occur during start-up and/or running operation.
It is yet another object of this invention to provide an improved radial lip seal that is suitable for use in high pressure (20 psi or greater) sealing environments, wherein the fluid pressures on the seal during use exerts a radial (sealing) force upon the seal lip relative to the rotary shaft to effect more complete sealing at the interface of the seal lip and the shaft.
It is still yet another object of this invention to provide an improved radial lip seal that is suitable for use in high pressure (20 psi or greater) sealing environments, wherein the radial lip seal, by design, causes radial loading of the lip relative to the rotary shaft, so as to minimize fluid leakage/by-pass at the seal/shaft interface.
Additional objects of this invention include the adaptation of the rotary lip seal of this invention for sealing of a rotary shaft of pumps and motor seals for automotive, marine, agricultural and industrial applications. .
The above and related objects are achieved by providing a system comprising a rotary lip seal and its associated retention gland, wherein the each of the seal and the gland are complimentary of the other within the environment of use. In the preferred embodiments of this invention, the rotary shaft sealing system of this invention is particularly adapted for the sealing of a rotary shaft in an environment wherein the hydraulic pressure upon the fluid within the system is at least 20 psi, or higher; and, the hydraulic pressures exerted upon the seal, at the interface of the seal and the rotary shaft, is subject to substantial variation and/or surges at the time of start-up and/or during operation/use of the rotary shaft.
The rotary lip seal of this invention is typically formed from a composition containing an elastomeric material (which can comprise a naturally occurring elastomeric material, a synthetic elastomeric material and/or any combination of such natural and synthetic materials). The materials of this composition are chosen and formulated for there resistance to abrasion, thermal stability and chemical resistance/inertness relative to fluids encountered in use. In the preferred embodiments of this invention, the materials of this composition can and generally include a lubricious agent or component (e.g. Kynar(trademark), a polyvinylidene fluoride; or Teflon(trademark), a polytetraflouroethylene), which upon frictional contact with the shaft, impart/transfer a lubricious agent to the shaft.
In one of the preferred embodiments of this invention, the radial lip seal of this invention, by design, has a shaft mounting hole/orifice wherein the inside diameter (ID) or such hole/orifice is smaller in diameter than the diameter of the rotary shaft. Accordingly, upon installation of the radial lip seal onto the shaft, the lip of the seal is xe2x80x9cpre-loadedxe2x80x9d relative to its interface with the shaft, thus, exerting positive sealing pressure upon the shaft at this interface.
In another of the preferred embodiments of this invention, the retention gland geometry, relative to the radial seal, causes fluid to be directed onto the seal, and thus positive hydraulic pressure, so at to instantaneously urge the lip of the seal against the shaft, thereby minimizing fluid leakage past the seal.
In another of the preferred embodiments of this invention (FIG. 3), the rotary lip seal comprises a composite, wherein a back-up element is associated with the seal to physically support the seal and prevent displacement and/or distortion of the seal lip relative to the rotary shaft at start-up; and, to further insure proper and complete seal alignment relative to the rotary shaft.
In another of the preferred embodiments of this invention (FIG. 3), the rotary lip seal incorporates a rotary dam comprising an internal lubricant, which upon erosion during pressure contact with the rotary shaft, imparts a lubricous film at the seal/shaft interface so as to shorten the break-in period of a new seal and, thus, facilitate initial leakage control at the interface of the seal and the rotary shaft.
In another of the preferred embodiments of this invention (FIG. 4), the rotary lip seal includes a pad or comparable means on the seal face, to urge the seal toward the downstream surface of the gland cavity.
In another of the preferred embodiments of this invention (FIG. 5), the retention gland internal profile is chamfered and/or otherwise modified to direct fluid flow onto the seal and thereby provide essential instantaneous application of hydraulic pressure to the seal lip at start-up.